Length of a linked list in C++

I have a struct A like the following:

struct A 
            {
            int v; 
            double weight;
            A* next;
            A(int x, double w, A* t){
                v=x;
                next = t;
                weight = w;
            }

        };

I am also saving these linked lists in a vector in the following manner:

typedef A* link; 
        vector<link>adj; 

Now, I would like to find the length of the linked list for adj[i]. I know that it is like traversing the linked list and incrementing a count to get the length of the linked list. For some reason I am not getting what I want. I was wondering, if someone could give me some pointers. Thanks